Method of separating isomeric monochloro-ortho-hydroxy-diphenyls



Aug. 8, 1933.

E. C. BRITTON ET AL METHOD OF SEPARATING ISOMERIG MONOCHLORCORTHOHYDROXYDIPHENYLS Filed Dec.

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guidut R11, chloro Z- ATTORNEY Patented Aug. 8, 1933 UNITED TA S PATENT OFFICE.)

h 1,921,727 1 I t. 7 METHOD OF SEPARATING ISOMERIC Mono- CHLORO-ORTHO-HYDROXY-DIPHENYLS Edgar C. Britton and Fred Bryner, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich., a Corporation of Michig an Application December 21, 1931. Serial N 0. 582,474

14 Claims.

of about 80 per cent, by weight, of 2hydroxy- 3-chloro-diphenyl to about 20 per cent of 2- hydroxy-5-chloro-diphenyl, is obtained. The crude reaction mixture may also contain unreacted 2-hydroxy-diphenyl and polychloro-Z-hydroxy-diphenyls, but such impurities are generally present in relatively small quantities. A

. practical method of separation of the compounds mentioned is much to be desired.

The present invention, then, consists of a method of separating 2-hydroxy'-'-3-chloro-di phenyl and 2-hydroxy-5 chloro-diphenyl from a mixture containing said compounds, such method being hereinafter fully described and particularly pointed outv in the claims, the an nexed drawings and the following description.

setting forth in detail several modes of carrying out the invention, such disclosed modes illustrating, however, but several of the various ways in which the principle of the invention may be used.

In the annexed drawings, Figure 1 is a freezing point-composition curve for the system 2-hydroxy-3-chloro-diphenyl' and 2-hydroxy-5-chloro-diphenyl; By comparing the freezing point of any mixture of the above mentioned isomeric compounds with thefreez'ing point-composition 0 curve diagrammed as Figure l, the composition of such mixture may be determined in the usual manner. Figure 2 is a flow sheet showing a series of plant operations which may be employed to separate the aforementioned isomeric com- 4 pounds according to the present method. It will be noted that unchlorinated 2-hydroxy-diphenyl 'and polychloro-2-hydroxy-diphenyls are separated from the isomeric monochloro-ortho-hy droxy-diphenyls during the course of operations carried out for the separation of said isomeric compounds from each other. As alternative procedure, a batch of crude chlorinated 'Z-hydroxydiphenyl may first be distilled to'separate a mixture of isomeric Lmonochloroa2 -hydroxy diphenyl from unreacted 2-hydroxy-diphenyl and from polychloro-2-hydroxy-diphenyls and said mixture of monochloro-Z-hydroiry-diphenyls may subsequently be separated into its components, according to procedure similar to that hereinafter described. M n

Although the mixture of isomeric monochloro- 2 -hydroxy-dipheny1s may be separated readily from the other components of the aforedescribed' reaction mixture through fractionally distilling the latter, 2-hydroxy-3 chloro-diphenyl and 2- hydroxy-fi-chlorordiphcnyl cannot conveniently be separated from each other by such .means, since the compoundsboil Withina few degrees of the'same temperature and tend to distill together, even when an efficient fractionating column is employed. in the operation.

Simple fractional crystallization of 'the free compounds from organicsolvents'does not afford a practicable means for separating, the above solvent.

We have also found'that 2-hydroxy-3-chloro--. diphenyl and 2-hydroxy 5-chloro-diphenyl may 5' be separated by means of an improved fractional crystallization method in which .the mixture is dissolved in a suitable alkali and the corresponding salt of 2-hydroxy-3chloroediphenyl, i. e. the. sodium, potassium, or barium salt, is crystallized from the solution, employing water, alcohol, or acetone as solvent. By acidifying the crystalline salt, 2-hydroxy-3chloro-diphenyl may be obtained-nearly pure, and may be purified still further "by redist'illation. from the crystallization, which will contain in excess of 20 per cent of the 5-chloro compound, is acidified witha mineral acid, and the mixture of 2-hydroxy-3-chloro diphenyl and 2-hydroxy- 5-chloro-diphenyl, which separates. after such 100 acidification, is fractionally crystallized to separate substantially pure 2-hydroxy-5 chloro-di Zphenyl therefrom. 1

' solvents. In practice we preferfirstfto crystal lize 2'-hydroxy-5-chloro-diphenyl from .a mixture 1.

The mother liquor of said compounds from the liquor in which they are formed, fractionally crystallizing a portion of the 2-hydroxy-5-chloro-diphenyl from a solution containing the last ,mentionedmixture of monochloro z-hydroxy-diphenyls, separating all solvent material from the mother liquor remaining after the last mentioned crystallization; and returning the residual? mixture-of isomeric monochloro-ortho-hydroxy diphenyls through the steps hereindescribed. I

3. In a method of separating 2-hy'droxy-3- chloro-diphenyl and 2-hydroxy-5-chloro-diphenyl from a mixture containing said compounds and 2-hydroxy-diphenyl and polychloro- 2-hydroxy-diphenyls, the'last named isomer being present in amount representingnot more than '20 per cent of the total weight of the least their combined chemical equivalent of aqueous sodium hydroxide, crystallizing a portion of the sodium salt of 2-hydroxy-3-chlorodiphenyl from theresultant solution, separating said crystalline salt from the aqueous mother liquor, dissolving the sodium salt of 2-hydroxy- 3-chloro-diphenyl in water, acidifying the resultant solution with a mineral acid to liberate 2-hydroxy-3-chloro-diphenyl as a free compound, separating the latter compound from the aqueous solution in which it is formed, distilling the 2-hydroxy-3-chloro-diphenyl under a pressure not exceeding 15 millimeters of mercury to obtain said compound in a purified form, acidifying the aqueous mother liquor (from which the sodium salt of 2-hydroxy-3-chlorodiphenyl was crystallized) to liberate a mixture of the previously mentioned monoch1oro-2-hydroxy-diphenyls as free compounds, separating the last mentioned mixture of free compounds from the liquor in which theywere formed, fractionally crystallizing a portion of the 2-hydr0xy- 5-chloro-diphenyl from a solution containing the last mentioned mixture of isomeric compounds, distilling solvent material from the mother liquor remaining after the last mentioned crystallization, and returning the residual mixture of isomeric monochloro-2-hyclroxy-diphenyls through the steps hereindescribed.

4. In a method of separating 2-hydroxy-3- chloro-diphenyl and 2-hydroxy-5-chloro-diphenyl from a mixture containing said compounds, the last named isomer being present in amount representing not'more than 20 per cent of the total weight of the monochloro-2-hydroxydiphenyls, the steps which consist in dissolving such mixture of hydroxy compounds in about 20 per cent more than its chemical equivalent of an aqueous, approximately 25 per cent sodium hydroxide solution, the mixture being maintained at a temperature sufiiciently high to permit complete solution during such operation, then cooling the solution to a temperature such that the sodium salt of 2-hydroxy-3-chloro-diphenyl crystallizes therefrom, and separating said crystalline sodium salt from the aqueous mixture. v

5. In a method of separating 2-hydroxy-3- chloro-diphenyl and 2-hydroxy-5-chloro-diphenyl from a mixture of said compounds, 'the last named isomer being present in amount representing notmorethan 20 per cent of the total weight of the monochloro-2-hydroxy-diphenyls, the steps which consist in dissolving such mixture in more than its chemical equivalent of an aqueous solution of a hydroxide selected from the group consisting of sodium, potassium and barium hydroxides, crystallizing and separating the corresponding metal salt of 2-hydroxy-3- chloro-diphenyl from the solution so formed,v treating said metal salt of 2-hydroxy-3-chlorodiphenylwith a strong mineral acid'to liberate 2-hydroxy-3-chloro-diphenyl as a free compound, separating the latter compound from the liquor in which it was formed, and distilling said compound under a pressure not exceeding 15 millimeters of mercury to obtain 2-hydroxy-3- chloro-diphenyl in a purifled'form.

r 6. In a method of separating 2-hydroxy-3- chloro -diphenyl and 2-hydroxy-5-chloro-diphenyl from a mixture of said compounds, the last named isomer being present in amount representing not more than 20 per cent of the total weight of the, monochloro-2-hydroxy-diphenyls,

the steps which consist in'dissolving such mixture-in about 20 per cent more thanits chemicalequivalent of' an aqueous, approximately 25 being maintained at about or above 65 C., during such operation, then cooling the solution'to about room temperature whereby the sodium salt of 2-hydroxy-3-chloro-diphenyl crystallizes from the solution, and separating said crystal-' line sodium salt from the aqueous mixture;

' '7. In a method of separating 2-hydroxy-3- chloro-diphenyl and 2-hydroxy-5-chloro-diphenyl from a mixture of said compounds, the.

representing more than 20 per cent of the combined weight of the two compounds mentioned,

the steps which consist in dissolving the above described mixture in an organic solvent selected from the group consisting of carbon tetrachloride, chloroform, ether, petroleum ether, alcohol, benzene and mixtures thereof, and crystallizing "per cent sodium hydroxide solution, the mixture a portion of the -2-hydroxy-5-chloro-diphenyl 3 from such solution.

9. In a method of separating 2-hydroxy-3- chloro -diphenyl and 2-hydroxy-5-chloro-diphenyl from a mixture containing said compounds, the last named isomer being present in amount representing not more than 20 per cent of the total weight of the monochloro-Z-hydroxy-diphenyls, the step which consists in fractionally crystallizing a salt of 2-hydroxy-3- chloro-diphenyl with a metal selected from the T40 group consisting of sodium, potassium, and

barium, from asolution containing said metal salt and the corresponding metal salt of 2- hydroxy-5-chloro-diphenyl dissolved in a medium selected from the group consisting of water, alcohol, acetone and mixtures thereof.

10. In a method of separating 2-hydroxy-3- chloro-diphenyl and 2-hydroxy-5-chloro-diphenyl from a mixture containing said compounds, the last namedisomer being present in group consisting of sodium, potassium, and

barium, from an aqueous solution containing said metal salt and the corresponding metal salt of 2-hydroxy-5-chloro-diphenyl.

11. In'a method of separating 2-hydroxy-3- chloro-diphenyl and 2-hydro-xy-5-chloro-di- ,phenyl from a mixture containing said compounds, the last named isomer being present in amount'representing not more than 20 per cent of the total weight of the mono-chloro-2- hydroxy-diphenyls, the step which consists in fractionally crystallizing the sodium salt of 2- hydroxy-3-chlorodiphenyl from an aqueoussolution containing the sodium salts of each of the above mentioned isomeric compounds.

12. The method of purifying 2-hydroxy-3- chloro-diphenyl which comprises dissolving a mixture containing said compound and 2-hydroxy-S-chloro-diphenyl, the latter being present in amount representing not more than 20 per cent of the total weight of the monochloro-2- hydroxy-diphenyls, in an excess of aqueous sodium hydroxide, crystallizing and separating the sodium salt of 2hydroxy-3chloro-diphenyl from the alkaline solution, treating said crystalline sodium salt with a strong mineral acid to liberate free 2-hydroxy-3echloro-diphenyl therefrom,-separating the latter compound from the liquor in which it is formed, and distilling said latter compound under a pressure not exceeding 15 millimeters of mercury to obtain purified 2- hydroxy-3-chloro-diphenyl as a distillate.

13. Inca method of separating 2 -hydroxy-3- chloro-diphenyl phenyl from a mixture containing the same, the

last named compound being present in amount representing not more than 20 per cent of the total weight of the monochloro-z-hydroxydiphenyls, the steps which consist in dissolving the mixture in an alkali, crystallizing out a salt of 2-hydroxy-3chloro-diphenyl and separating and 2 hydroxy 5 chloro-dithe same from the mother liquor, acidifying the mother liquor, separating the phenols from the acidified mixture, fractionally distilling the phenolic mixture to separate a mixture consisting substantially of 2-hydroxy-3-chloro-dipheny1 and 2-hydroxy-5chloro-diphenyl in which the latter compound is present in amount representing at least 20 per cent; of the total weight of total weight of the monochloro-2-hydroxy-diphenyls, to separate 2-hydroxy-5-chloro-diphenyl therefrom. u

. EDGAR C. BR'I'ITON. I FRED BRYNER. 

